1. Field of the Invention
The invention relates to apparatuses and methods for treatment of conditions of the cranial vasculature, and more specifically to modulating function of particular neural structures in the vicinity of the ear for treatment of stroke and other conditions.
2. Description of the Related Art
Stroke is the most common cause of physical disability and the third most common cause of death in the United States. Nearly 900,000 cases of stroke occur each year in the United States, costing $69 billion in healthcare costs. Worldwide, there are nearly 15 million cases of stroke annually; the cost of healthcare services and lost productivity on such a scale is incalculable. Most cases of stroke are caused by loss of blood flow to the brain because of occlusion of a cerebral artery or carotid artery. Cerebral artery occlusion commonly results from (1) a blood clot that is carried by the blood flow into an artery in which it becomes lodged or (2) by formation of a blood clot upon an area of atherosclerotic plaque inside the artery. Loss of blood flow by either mechanism, or by any of several less-common mechanisms, deprives areas of the brain fed by the artery of nutrients and oxygen, leading to cell death and tissue necrosis.
The emergency treatment of stroke is limited. Only one drug, the thrombolytic tissue plasminogen activator (Alteplase), has been approved for the treatment of acute stroke in the United States. Alteplase acts to dissolve blood clots such as those that occlude cerebral and carotid arteries, causing stroke. As a result, Alteplase can also cause severe intracranial hemorrhage, which is its most serious complication. In order to reduce the chance of intracranial hemorrhage, Alteplase is subject to numerous restrictions that ultimately limit its use to only about 3% of all stroke patients.
In addition to Alteplase, endovascular techniques employing intra-arterial catheters are used to treat acute stroke. Endovascular techniques, based largely on retrieval of the blood clot from the cerebral or carotid artery or else local administration of thrombolytic drugs onto the blood clot, are costly and dangerous, and their use is limited to large hospitals that have highly-trained endovascular physicians on staff. Accordingly, only several thousand stroke patients appear to be treated with endovascular techniques each year in the United States.
A possible treatment of stroke that is currently under development is electrical stimulation of the sphenopalatine ganglion. This potential treatment involves placement of a stimulator rod through the roof of the mouth (hard palate) into the vidian canal, which leads to the sphenopalatine ganglion. This device and method has a number of drawbacks. By inserting the stimulator rod through the mouth into the vidian canal, there is a risk of introducing dangerous oral bacteria into the bones of the face. In addition, the blind insertion of the stimulator rod into the confines of the vidian canal (which not only leads to the sphenopalatine ganglion but also contains the vidian artery and nerve) of the hard palate risks inducing bleeding or direct nerve injury. Furthermore, placement of the stimulator rod requires specialized training and equipment. An additional concern associated with this method is that stroke patients commonly have difficulty swallowing as part of their neurological injury. Procedures requiring implantation of foreign bodies in the mouth, as required by this method, may lead to aspiration injury in patients with airways already compromised by the neurological injury from stroke. Finally, this device and method only stimulates the sphenopalatine ganglion and its immediate connections, which in animals has a small effect on blood flow to the brain. In comparison, stimulation of the entire facial nerve—which activates the sphenopalatine ganglion as well as several other nerves and ganglia—has a much more profound effect on blood flow to the brain.
Because of the magnitude of the disease and the limited treatments for it, a significant unmet medical need exists in acute stroke. Thus, there is a need for a solution that solves the problems with current acute stroke treatments noted above, and that: (a) does not cause intracranial hemorrhage, aspiration injury, bleeding and nerve injury in the vidian canal, or facial bone infection; (b) does not require highly-trained endovascular physicians or specialized training for use; and (c) can be placed under direct visualization or else is non- or minimally-invasive.